The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 21, 1999
Filed:
Dec. 23, 1997
Kenji Takato, Kawasaki, JP;
Fujitsu Limited, Kanagawa, JP;
Abstract
Disclosed is a method for communication with no power feed in an exchange. (1) A calling subscriber unit transmits a special service code designating the disuse of a direct current loop together with the numeric information on the called subscriber unit to the exchange after formation of a direct current loop. (2) When the special service code is received, an on-hook transmission state in which the transmission and reception of an alternating current signal is possible between the subscriber line interface circuit and the calling subscriber unit even if no direct current loop is formed is established in the subscriber line interface circuit to which the calling subscriber unit which has transmitted the special service code is connected. (3) The calling subscriber unit disconnects the direct current loop, and the exchange maintains the speech path between the calling subscriber unit and the called subscriber unit even after the direct current loop is disconnected. (4) An alternating current signal is transmitted and received between the subscriber line interface circuit and the calling subscriber unit in the state in which no direct current loop is formed.